This research project is a multidisciplinary program for the study of the microcirculation. The principal emphasis is on study of the regulation of blood flow through the capillaries and arterioles and the mechanisms whereby substances are exchanged between the blood and tissues. The local regulatory mechanisms (metabolic and myogenic) will be examined in detail through a variety of experimental studies. The behavior of these mechanisms will be characterized with the aid of analytical models. A close working relationship between the experimental and analytical phases of the study is planned. A similar approach will be taken in studies of exchange, with experimental and theoretical aspects closely related. The program will work toward a comprehensive model of regulatory and exchange phenomena in the microcirculation. The program also includes a core facility for development of new techniques for the study of circulation.